U.S. patent number 5,372,452 [Application Number 08/022,057] was granted by the patent office on 1994-12-13 for power trowels.
Invention is credited to James A. Hodgson.
United States Patent |
5,372,452 |
Hodgson |
December 13, 1994 |
**Please see images for:
( Certificate of Correction ) ** |
Power trowels
Abstract
An improvement to power trowels having a power unit, a rotatable
shaft, a plurality of trowling blades mounted to spider arms, and a
shroud for shielding the blades. The blades are formed of spring
steel and are fixedly mounted to the spider arms. A throttle
control unit is removably mounted to the trowel and may be
extendably mounted to an adjustable extendible pole.
Inventors: |
Hodgson; James A. (Fargo,
ND) |
Family
ID: |
21807593 |
Appl.
No.: |
08/022,057 |
Filed: |
February 24, 1993 |
Current U.S.
Class: |
404/112;
404/97 |
Current CPC
Class: |
E04F
21/248 (20130101) |
Current International
Class: |
E04F
21/00 (20060101); E04F 21/24 (20060101); E01C
019/22 () |
Field of
Search: |
;404/83,84.05,84.1,84.5,96,97,101,102,118,120,112 |
References Cited
[Referenced By]
U.S. Patent Documents
Other References
Forshel, "The Bantam, 20" Hand Held Power Trowel. .
Structron, "Superhandle II, The Next Generation of Fiberglass
Extension Handles"..
|
Primary Examiner: Britts; Ramon S.
Assistant Examiner: Lisehora; James A.
Attorney, Agent or Firm: Westman, Champlin & Kelly
Claims
What is claimed is:
1. An improvement to trowling machines having a power unit, a
rotatable shaft extending downward therefrom, a plurality of
trowling blades, mounting means for mounting the trowling blades to
the rotatable shaft, and a shroud for shielding the blades, the
improvement comprising:
the blades being mounted to the mounting means at a selected
pitch;
an attachment member fixed to the exterior of the shroud;
a manually operated throttle control including a manual grip and
control element and having a short length pole, mounting means on
the short pole for removably mounting the short pole to the
attachment member on the shroud to control the power unit and to
permit guiding the shroud from adjacent the shroud;
a power unit control coupled to the control element to control the
power unit; and
an elongated pole having first and second ends and means for
mounting a first end of the elongated pole to the mounting member
on the shroud when the short pole is removed, and means for
receiving the short pole at the second end of the elongated pole,
wherein the throttle control is extendably mounted by the elongated
pole.
2. The trowling machine of claim 1 wherein the blades are formed of
spring steel.
3. The trowling machine of claim 1 wherein the blades are planar
and are mounted to the mounting means with the blade plane at a
pitch angle of 12 degrees.
4. The trowling machine of claim 1 wherein the elongated pole is
pivotally mounted and is pivotal up to 100 degrees in motion.
5. The trowling machine of claim 1 wherein the power unit control
is electrically actuated by the throttle control means.
6. The trowling machine of claim 5 further including a coupling to
electrically couple the throttle control to the power unit control
means.
7. The trowling machine of claim 1 wherein the shroud is made of
plastic.
8. The trowling machine of claim 1 wherein the mounting means
comprise arms extending radially from the shaft, the blades each
having a support positioned laterally of a longitudinal center line
of the blade and the support being mountable to the mounting means,
such that each of the blades can be turned end for end on its
respective support to provide a different width of blade
rotationally trailing the mounting means.
9. An improvement to trowling machines having a power unit, a
rotatable shaft extending downward therefrom, a plurality of
trowling blades having first and second ends, mounting means for
mounting the trowling blades to the rotatable shaft, and a shroud
for shielding the blades, the improvement comprising:
the blades each being mounted to the mounting means selectively in
a first position with a first end of the respective blade adjacent
an outer periphery of the shroud and in a second position with a
second end of the respective blade adjacent the outer periphery of
the shroud, wherein the blades are formed of spring steel and are
fixed at a pitch angle between the range of 5 degrees and 20
degrees from horizontal during operation;
at least one throttle control connection being located on the power
unit;
throttle control means removably mounted to one of the throttle
control connections;
power unit control means mounted to the power unit to control the
power unit to rotate the mounting means and blades, each blade
having a different length rotationally trailing the mounting means
in its respective first and second positions.
10. The trowling machine of claim 9 wherein the blades are planar
and are mounted to the mounting means with the blade plane at a
pitch angle of 12 degrees.
11. The trowling machine of claim 9, wherein the throttle control
means is extendably mounted to be shrewd by a replaceable,
extendible pole.
12. The trowling machine of claim 11, wherein one end of the
extendible pole is pivotally mounted to the shroud and pivots up to
100 degrees in motion.
13. The trowling machine of claim 9 wherein the power unit control
means is a servo motor mounted to the power unit.
14. The trowling machine of claim 9 wherein the power unit control
means is remotely actuated.
15. The trowling machine of claim 9 wherein the power unit control
means is electrically actuated by the throttle control means.
16. The trowling machine of claim 15 further including a coupling
means to electrically couple the throttle control means to the
power unit control means.
17. The trowling machine of claim 9 wherein the shroud comprises a
lower retaining ring and an upper guard portion, the lower
retaining ring having four substantially flat sections spaced
equally around the periphery of the ring.
18. The trowling machine of claim 9 wherein the shroud is made of
plastic.
19. The trowling machine of claim 9 wherein each of the blades is
pivotally mounted to its mounting means about a generally upright
bolt, each of the blades having a channel means that fits around
the mounting means and which can be pivoted about the bolt
180.degree. between the first and second positions for
operation.
20. An improvement to trowling machines having an internal
combustion power unit, a rotatable drive shaft extending downward
therefrom, a plurality of trowling blades, mounting means for
mounting the trowling blades to the rotatable shaft, and a shroud
for shielding the blades, the improvement comprising:
the blades being mounted to the mounting means, the blades being
formed of flexible spring steel and being mounted at a pitch of
angle between 5 and 20 degrees from horizontal as they move;
a plurality of control connections located on the power unit
including a throttle control connection to control speed of
operation;
a throttle control removably mounted to the throttle control
connection;
a power unit control removably mounted to the power unit to control
the power unit, the power unit control being electrically actuated;
and
the shroud comprising a lower substantially vertical skirt forming
a retaining ring and upper guard wall portion tapering upwardly
from the skirt and extending around the entire ring to overlie and
enclose regions above the blades with the guard wall, the power
unit being mounted at an upper end of the upper guard wall,
21. The trowling machine of claim 20 wherein the lower vertical
skirt is a peripheral skirt and has four substantially flat
sections spaced equally around a periphery of the skirt, the blades
passing closely adjacent to an inner surface of the skirt at the
flat sections to permit trowling close to a vertical surface at the
flat sections of the skirt.
22. The trowling machine of claim 20 wherein the shroud is made of
plastic.
23. The trowling machine of claim 20 wherein the mounting means
comprise generally radial arms, the blades having a length
extending radially and a lateral width, a separate support fastened
to each blade and positioned on the blade offset from the
longitudinal axis, the support being mountable on the mounting
means in two positions 180.degree. apart to provide a different
width of the blade to trail the arm in each of the two positions to
provide a different width of blade trailing the mounting means in
each of the two positions.
24. An improvement to trowling machines having a power unit,
rotatable shaft extending downward therefrom, a plurality of
trowling blades, mounting means for mounting the trowling blades to
the rotatable shaft, and a shroud for shielding the blades, the
improvement comprising:
the blades being mounted to the mounting means at a selected
pitch;
an attachment member fixed to the exterior of the shroud; a
manually operated throttle control including a manual grip and
control element and having a short length pole, mounting means on
the short pole for removably mounting the short pole the attachment
member on the shroud to control the power unit and to permit
guiding the shroud from adjacent the shroud; and
a power unit control coupled to the control element to control the
power unit; and
an extendible elongated pole of substantial length, said extendible
elongated pole having two ends and having means for mounting at one
end matching the means for mounting on the short pole, and an
opposite end of the extendible elongated pole having a coupling to
receive the means for mounting on the short pole to permit the
manual grip to control and guide the unit at an outer end of the
extendible elongated pole.
Description
BACKGROUND OF THE INVENTION
The present invention relates to an improvement to power trowling
machines and, more particularly, relates to making the trowling
machine lightweight and with fixed pitch spring steel blades,
therefore making the machine very easy to use.
Trowling machines for finishing concrete or other surfaces have
been known for many years. Common to these trowling machines are a
centrally mounted power unit, such as an internal combustion
engine, attached to a handle for holding and maneuvering the
machine, a gear reducing unit connected to the power unit and a
trowling assembly which rotates about a vertical axis beneath the
power unit. The rotatable trowling assembly commonly comprises a
hub mounted on a vertical shaft which is rotatable by the power
unit through the gear reducing unit, and a plurality of trowling
blade carriers in the form of arms extending radially from the hub.
Typically, each carrier adjustably supports a trowling blade which
extend radially and are usually inclined at a small pitch angle
from the horizontal plane, with their trailing edges lowermost. The
blades are effective to finish smoothly a surface of wet concrete
or the like.
Exemplary of early trowling machines are U.S. Pat. No. 4,629,359 to
Sengupta and U.S. Pat. No. 4,198,178 to Carlstrom et al. Both the
Sengupta and the Carlstrom et al. patent disclose power trowels
having adjustable pitched blades. U.S. Pat. No. 4,046,483 to
Sutherland discloses a power trowel having an adjustable blade
length and an adjustable blade pitch.
Traditionally, finishing concrete was a time consuming and delicate
job. To create a desirable finish to the concrete, surface pores on
the concrete must be closed by means of a trowling action either by
hand or a trowling machine. The surface pores must be closed
without disturbing larger aggregates that lie just below the
surface that form a wearing plate. If this wearing plate is
disturbed, the concrete will be subject to premature
deterioration.
The previously mentioned known power trowels are typically of such
a substantial weight that to place them on a wet concrete surface
shortly after it has been poured will destroy the wearing plate and
cause premature deterioration of the concrete. The operator must
wait until the concrete substantially sets. Waiting for the
concrete to substantially set up extends the finishing time, which
in turn correlates to high labor costs wasted while waiting for the
concrete to set. Also because of the size of the previously known
power trowling machines, a substantial amount of operator strength
is required to operate one of these machines. Furthermore, a great
deal of experience and skill is needed to effectively operate them
because the trowling blades of these known power trowling machines
need to be adjusted in order to achieve a proper finish to the
concrete. Each adjustment of the trowling blades has an effect on
the finish of the concrete. Too steep of a pitch will dig too
deeply into the wearing plate, thus causing premature deterioration
of the concrete. Not enough pitch may not close the surface pores,
thus creating a rough and incompletely finished surface.
SUMMARY OF THE INVENTION
The present invention provides a light weight power trowling
machine that has fixed pitch spring steel blades thus making the
machine very easy to operate. In a preferred embodiment of the
present invention, a power trowling machine having the same basic
elements as previously known power trowels is improved by fixedly
mounting trowling blades onto mounting means. The trowling blades
are not adjustable and are made of spring steel instead of the
standard high tensile steel. A removable throttle control means is
provided to control the speed and operation of the trowling
machine. A plurality of throttle control connections are located on
the power unit to accommodate left and right handed operators and
to allow the operator a choice of where to mount the throttle
control. The throttle control means may be mounted directly to one
of the throttle control connections or can be mounted to the end of
an extendible pole which in turn is connected to one of the
throttle control connections. Thus, an operator may operate the
improved power trowel from extended distances, such as 10 or 20
feet away from the concrete surface being finished. A power control
means is mounted on the power unit and is electrically actuated by
the throttle control.
A plastic shroud is provided to shield the blades during their
operation. The shroud is comprised of a lower retaining ring and an
upper guard portion. In order to allow the improved power trowel to
finish near walls or edges, the lower retaining ring portion has
four flat sections spaced evenly about the periphery of the lower
retaining ring. The four flat sections allow the trowling blades to
come within one quarter inch from the edge of the lower retaining
ring.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a side elevational view of a power trowel made according
to the present invention;
FIG. 2 is a schematic view of the drive assembly of the power
trowel;
FIG. 3 is a bottom plan view of the power trowel;
FIG. 4 is an end view of the trowling blades showing the angle of
pitch;
FIG. 5 is a side elevation view of the power trowel utilizing an
extended pole;
FIG. 6 is an enlarged perspective view of a throttle control;
FIG. 6b is a top plan view of a portion of the throttle
control;
FIG. 6c is a sectional view of a portion of throttle control
mounting to an extendible pole;
FIG. 7 is a schematic plan view of a preferred alternative
embodiment;
FIG. 8 is a perspective view of an preferred alternative
embodiment; and
FIG. 9 is a sectional view taken along line 9--9 of FIG. 8.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The present invention comprises a lightweight, easy to use power
trowel shown generally at 10 in FIG. 1. A power unit shown
generally at 11 powers the trowling machine 10. The power unit 11
utilized in the embodiment illustrated is a two stroke engine, but
it should be noted that any power unit developing sufficient power
to rotate trowling blades on wet concrete may be used, such as an
electric motor or a four stroke engine.
As illustrated schematically in FIG. 2, a servo motor 14 is mounted
to the power unit 11. A throttle 21 is connected to the servo motor
14 to control the power unit 11 as will be described later. An
electric starter 15 is mounted to the power unit 11 to provide the
power trowel 10 with a simple way of starting. A battery pack 25
comprising rechargeable batteries is part of the electric starter
15. The batteries 25 are charged when the power trowel 10 is in use
or they can be charged externally as will be described below. A
clutch assembly 13 is positioned below the power unit 11 and
operates in a commonly known manner. A gear reducing means 16 is
positioned below the clutch assembly 13, and in the preferred
embodiments has an 80 to 1 gear reduction. For the present
invention, any type of gear reduction less than 100 to 1 would be
acceptable.
A rotatable drive shaft 18 extends below the gear reducer 16 and
provides a rotating means for the trowling unit 10. A rotating
assembly 17, as seen in FIG. 3, is attached to the rotatable drive
shaft 18. The rotating assembly 17 comprises a hub 19 and a
plurality of arms 20, generally called spider arms, connected to
the hub 19. Any number of spider arms 20 may be used, but in the
embodiment illustrated there are four spider arms 20.
A trowling blade 22 is connected to each of the spider arms 20. The
trowling blades 22 of the present invention are formed from thin
spring steel which permits the blades 22 to flex with respect to
their supports. Each of the blades 22 is fixedly mounted to the
spider arms 20 by common fastening means such as a hitch pin
assembly 27 as shown in FIG. 4. Each trowling blade 22 has a
channel 23 attached to its upper or back side. This channel 23 fits
around the spider arm 20 and has holes to receive the hitch pin
assembly 27, which fastens the blade 22 to the spider arm 20. The
channel 23 in the preferred embodiment is retained along the
longitudinal axis of each blade 22.
As the blades 22 rotate, each blade has a leading edge 24 and a
trailing edge 26. The blades 22 are fixedly mounted to the spider
arm 20 so that the leading edges 24 are raised and the plane of the
blades 22 are 12 degrees from horizontal, as is illustrated in FIG.
4. Thus, when rotating, the trailing edges 26 of blades 22 will
contact the concrete surface while the leading edges 24 remain off
the concrete surface.
A plastic shroud 28 is attached to the power unit 11 and extends
downwardly and outwardly, encircling the path traveled by the
blades 22. Plastic is used because it is light weight, easier to
mold into different shapes or forms for the shroud 28, and it is
resistant to the corrosive additives normally found in concrete.
Plastic is also used because of the integral coloring available
which enhances the appearance of the machine as opposed to painted
metal which has a tendency to chip. It should be noted that the
spider arms 20 may also be made of plastic and the casing of the
power unit 11 may be made of plastic, but use of other materials
for both of these components is acceptable. The shroud 28 has two
portions; a lower retaining ring 30 at the periphery of the blade
travel path, and an upper guard portion 32 that surrounds the
rotating assembly 17 and tapers from the lower retaining ring 30 up
to the power unit 11. The upper guard portion 32 may be formed from
a solid plastic mold or it may have viewing holes as illustrated in
the Figures so that the operator may see the rotation of the blades
22.
The lower retaining ring 30 is formed to have four substantially
flat portions 34 spaced equally around the outer periphery of the
lower retaining ring 30 as illustrated in FIG. 3. These flat
portions 34 allow an operator to get within one-quarter inch of the
edge of the retaining ring and thus close enough to a form or wall
so as to virtually eliminate the need for hand trowling. In
previously known power trowels, the closest an operator could get
was often two or three, and sometimes four inches from a wall, thus
requiring substantial hand trowling to finish the job properly. A
number of D handles 36 are spaced evenly across the guard portion
32 of the shroud 28 for an operator to hold while using the power
trowel 10 in a non-extended manner. There are three handles 36
spaced about the shroud 28 in the preferred embodiment. Mounting
members or ears 38 are fixed to the shroud 28. Two ears 38 are
shown in FIG. 1, but preferably there are three such ears spaced
120 degrees apart on the shroud. A mower unit throttle control 40
attaches to one of the mounting ears 38 and has controls coupled by
a coiled cord 48 to the power unit controls to control the speed of
the power trowel 10. An extendible pole 50, to be described in more
detail below, may be mounted to one of the mounting ears 38 in
place of the throttle control 40 with the throttle control 40 then
being attached to the other end of the extendible pole 50. This
allows for operation of the power trowel 10 from an extended
distance.
An on/off switch 42, to turn the machine on, and a start button 43
to activate the electric starter 15 are mounted on the throttle
control 40 as is illustrated in FIG. 6. The on/off switch 42 acts
as a kill switch. If the switch 42 is on and the trowling machine
10 is running, when the switch 42 is turned to off, the machine
will be stopped. A spring loaded trigger control 44 is provided on
the throttle control 40 to control the speed of the power unit 11
and thus the speed of rotation of the trowling blades 22. A spring
66 is provided to return the trigger control 44 to its home
position when it is released. The trigger control 44 is a variable
speed controller in which the blades 22 rotate at speeds dependant
upon the amount that the trigger is pulled.
A potentiometer 46, which is shown schematically in FIG. 6, is
mounted in the throttle control 40 and enables the servo motor 14
to control the throttle 21 of the power unit 11 electrically rather
than by a mechanical connection. A cable 67 directly couples the
potentiometer 46 to the spring loaded trigger 44. When the trigger
44 is pulled, the cable 67 moves the potentiometer 46 thus changing
the effective resistance of the potentiometer 46. A servo driver 47
is mounted adjacent the potentiometer 46 in the throttle control 40
to drive the servo motor 14.
The coiled cord 48 electrically couples the throttle control 40 to
the power unit 11 to enable the trigger control 44, potentiometer
46 and servo driver 47 to electrically control the servo motor 14,
and to couple the on/off switch 42 and the start button 43 to the
electric starter 15. The throttle control 40 has a yoke attachment
51 for attaching directly to the mounting ears 38. The yoke
attachment comprises a pair of spaced mounting tabs 55 similar in
size to the mounting ears 38 as illustrated in FIG. 6b. The tabs 55
are spaced apart enough to fit around the mounting ears 38. Pin
holes 53 to secure the throttle control 40 to the mounting ears 38
are provided in the tabs 55. The yoke attachment 51 is of a size to
fit into the extendible pole 50, to be described.
A charging receptacle 57 is also provided on the throttle control
40. The charging receptacle is for charging the battery pack 25, or
if an electric motor is chosen as the power unit, for charging the
batteries associated with the electric motor.
The throttle control extendible pole 50 may be used to control the
power trowel from extended distances such as 10 or 20 feet. The
distance the pole is extended to is dependant upon the integrity of
the pole. The stronger the pole is the farther it can be extended.
The extendible pole 50 connects to one of the mounting ears 38 at
one end and receives the throttle control 40 yoke attachment 51 at
the other end. As illustrated in FIG. 6c, the yoke attachment 51 is
inserted into aperture 58 of the extendible pole 50. Retaining pin
holes 59 are provided in the walls of the extendible pole 50 as
shown. The yoke attachment 51 is inserted approximately three
inches into aperture 58 where pin holes 53 of the tabs 55 align
with pin holes 59 of the extendible pole 50. When the pin holes
align, a cotter pin or other retaining pin 65 is inserted. The
extendible pole 50 used in the embodiment illustrated in FIG. 5 is
the Superhandle II by Structon, but any such extendible pole may be
used.
The coiled cord 48 stretches to extend along the extendible pole 50
and is retained by commonly known retaining means so as to not drag
down into the concrete. The extendible pole 50 has a range of
motion that encompasses approximately 100 degrees of movement in a
vertical plane wherein the upper rotation is limited when the
extendible pole 50 strikes the power unit 11 and the lower limit is
set when the extendible pole 50 strikes the concrete surface.
In operation, once a concrete surface that is in need of finishing
has begun to set, the present invention may be utilized. The power
trowel 10 made according to the present invention will be able to
begin finishing the concrete well in advance of the time that
conventional power trowels and operator would be able to get out
onto the concrete surface. Often times, the present invention may
be used sooner than traditional kneeboards and hand trowling
because with the extendible pole 50 an operator does not need to
step or kneel on the concrete surface at all. Before starting use,
the operator must decide if the throttle control 40 should be
mounted directly to the power trowel 10 or if the extendible pole
50 is going to be used. Once the throttle control 40 is mounted to
either the power trowel 10 or the extendible pole 50, the on/off
switch 42 on the throttle control 40 may be switched, turning the
machine on.
With the on/off switch 42 set to on, the machine may be started by
depressing the start button 43. With the machine now on, pulling of
the trigger control 44 causes the blades 22 to rotate. This
function is achieved electrically through the potentiometer 46, the
servo driver 47 and the servo motor 14. As the trigger control 44
is pulled, the potentiometer 46 is moved by the cable 67, thus
changing the effective resistance of the potentiometer 46. By
changing the resistance of the potentiometer, the current sent to
the servo motor 14 by the servo driver 47 is changed. Increasing
the resistance of the potentiometer reduces the current sent to the
servo motor 14, and reducing the resistance of the potentiometer
increases the current sent to the servo motor 14. Current to the
servo motor 14 is provided from the servo driver 47 through the
coiled cord 48. The servo motor 14 in turn drives the throttle 21
of the power unit 11 to a set position proportional to the current
received by the servo motor 14. This electrical arrangement is used
in place of a traditional mechanical throttle control, where a
cable is run from the throttle trigger to the carburetor of the
power unit, because the reliability of the electrical control
system is far greater than the mechanical system when used at
extended distances. It should be noted that other connecting
methods may be used, such as an air piston drive system or other
commonly known extendible control systems.
With the blades 22 rotating, the trailing edge 26 of the blade 22
is contacting the concrete surface and supporting the power trowel
10. With the power trowel 10 on and the blades 22 rotating, the
power trowel will virtually hover in place. This is due in part to
the fact that the power trowel of the present invention is
lightweight and does not provide a great deal of torque. It is also
due to the fact that the center of gravity of the power trowel 10
is directly above the axis of rotation of the trowling blades 22,
shown at 52 in FIG. 2. The gear reduction means 16 lies on the axis
of rotation 52 of the blades as does the drive shaft 18, the clutch
assembly 13, and the power unit 11. Because the power trowel 10
does not pull hard in any direction, the power trowel of the
present invention is very easy to manipulate.
As previously stated, with the trowling blades 22 rotating, the
trailing edge 26 of each blade is contacting the concrete surface.
Because spring steel trowling blades are used, adjustment of the
blade pitch is not necessary. The spring steel blades deflect to
form a proper finished surface. In the embodiment illustrated, each
blade is 4 inches wide and 0.0025 inches thick. With this blade
size, the weight displacement ratio for the power trowel 10 is 1.25
oz/in.sup.2 of blade area. To get out onto the concrete surface
even earlier, the weight displacement ratio can be reduced. This
can be accomplished by using a blade 6 inches wide and 0.0015
inches thick. This reduces the weight displacement ratio to 1.125
oz/in.sup.2.
In a preferred alternative embodiment, illustrated in FIG. 7, three
power trowels of the type described are connected together in a
triangular configuration. Each of these power trowels is similar to
the power trowel 10 described with reference to FIGS. 1-6b.
Corresponding numbers will be used to identify corresponding parts.
Connecting bars 60 connect the three trowling machines 10 in
triangular form. A servo motor 14 is mounted to each of the power
trowels 10. A radio frequency receiver 61 is attached to the power
trowels 10 and is coupled to the servo motors 14. Instead of
directly coupling the servo motor to the throttle control means 40,
the servo motors 14 are remotely operated. A radio frequency
transmitter 62, of the type commonly known in radio control
modeling, may be used to operate the power trowels 10. This
configuration would allow an operator to finish larger surface
areas from distances greater than possible with the extendible pole
50.
In another preferred alternative embodiment, a way to vary the
trowling force applied to the concrete by the trowling blades is
provided. The blades of this preferred alternative embodiment are
illustrated in FIGS. 8 and 9. This embodiment provides trowling
blades 70 having channels 72 attached to an upper or back side 71
of each blade 70. The channels 72 fit around spider arms 73 that
rotate the blades 70. The channels 72 of the alternative embodiment
may be formed anywhere along the upper or back sides 71 of the
blades 70.
In FIG. 8, the blades 70 have an edge 74 touching the concrete
surface and incline up and away from the concrete to an edge 76. In
the illustrated preferred alternative embodiment, the channel 72 is
placed closer to the edge 76 than the lower, trailing edge 74. In
this position, the blade 70 will flex more than if the channel were
midway on the blade 70, thus allowing an operator to begin
finishing the concrete sooner than if the channel were in the
middle of the blade 70.
To increase the amount of trowling force applied to the concrete by
the blades 70, the channel 72 should be placed nearer to the edge
74. By rotating the blades 72 180 degrees, or end for end, the same
blades may be used to finish concrete that has set up longer and
thus requires a more rigid blade for satisfactory trowling.
The mounting arrangement of this preferred alternative embodiment
allows the blades 70 to be rotated end for end. A substantially
vertical pin 78 having a cotter pin 80, a head 82, a washer 84
mounted on the pin 78 and a compression spring 86 slidably mounted
on the pin 78. The base of the blade 70 is bored out to receive the
head 82 of the pin 78 which is fused to the blade 70. The cotter
pin 80 is provided to retain the washer 84 on the pin 78 which in
turn retains the compression spring 86 on the pin 78.
To rotate the blade 70 end for end, the blade 70 is pushed downward
away from the spider arm 73 until 10 the channel 72 is clear of the
spider arm 73. When the channel 72 is clear of the spider arm 73
the blade 70 may be rotated. When the blade has been rotated 180
degrees, the channel will again fit around the spider arm. The
compression spring 86 tends to pull the blade 70 toward the spider
arm 73 thereby keeping the blade in close proximity to the spider
arm 73.
This preferred alternative embodiment makes it easy to change the
amount of trowling force applied to a concrete surface. The pin
arrangement illustrated also makes it easy to replace blades. To
replace the blades 70, the cotter pin 80 is removed, the washer 84
is then removed from the pin 78 and the spring 86 is then slide off
of the pin 78. The blade 70 is then replaced by a new blade.
Although the present invention has been described with reference to
preferred embodiments, workers skilled in the art will recognize
that changes may be made in form and detail without departing from
the spirit and scope of the invention.
* * * * *